Field of the Invention
This invention relates to a method for making a tubular bushing from flat stock, and particularly to a method for making a fully flanged bushing with interlocking features.
Description of the Related Art
Bushings, including flanged bushings, may be formed by processes such as roll forming, draw forming, spinning, or stamping, however, a major disadvantage experienced with many of these processes is the extensive material stretching which the workpiece must undergo in order to achieve its final form. Some processes, such as draw forming in particular, deform the workpiece so extensively that they grossly alter or deform the material's grain structure creating a part with internally dissimilar material properties due to work (strain) hardening.
Another disadvantage of these processes occurs when a closed annular form is flanged in a radial direction. Since the area of a circular flanged region is related to its radius through the formula: Area=Pi*Radius2, the flange material must necessarily stretch to cover an ever increasing area as the flange's radial distance increases. This causes excessive stretching in flanged region which may be exhibited by thinning, wrinkling, or even rupture of the material in the flanged portion of the annular form.
To avoid this issue, a portion of the annular form may be severed prior to formation of the flange. This creates a discontinuity in the flanged material that progressively enlarges with the increase in the flange's radius. This discontinuity appears as a ‘V’ shaped gap shown in FIG. 1 (Prior Art) which serves to relieve the excessive stretching by reducing the area of material coverage in the flange. However, the use of a discontinuous form in this manner has in inherent drawback, since the discontinuity lacks adjacent material support, it will tend to concentrate stresses and loads directly into the root of the discontinuity. This in turn may cause the separation or decoupling of the bushing, and release of any part contained therein.
The invention described herein provides a solution to the problems described above.